Photochemical production of olefinic hydrocarbons



Patented Oct. 13, 1953 PHOTOCHEMICAL OLEFINIC HY PRODUCTION 01'! OCARBQNS Henry G. Schutze and Harry E. Cier, Baytown,

by mesne assignments, to-

Standard Oil Development Company, Elizabeth, N. J., a corporation of Delaware No Drawing. Application March, 24,1951,

Serial No. 217,402

11 Claims. (Cl. 204162) The present invention is directed to a method for producing olefins. invention is concerned with the production of feed.

The temperature employed in the present invention may suitably range from about 100 F. to 750 F. with a preferred temperature in the rangefrom about 200 to about 500 F. Temperatures lower than 10 F. have no particular efiect on the course of the reaction but higher temperatures than the maximum may result in cracking reactions taking place.

The parafiinic hydrocarbon employed in the butanes, the pentanes and the hexanes. butane forms the preferred feed stock present invention. Likewise the normal parafi'i-nic hydrocarbons are preferred to the isoparafiinic hydrocarbons. Normal pentane and f the vapor pressure, light absorption characteristics. and energy content in the activated state. What- In selecting a metal sensitizer and a source of radiant energy for the reaction, the following conditions mm. of mercury-at a temperature below about 650 F.

(B) The radiant (Cl The sum of the energy of the resonance frequency absorbed by the metal sensitizer and of the energy-of the metal-hydrogen hand must paraifin 04:1 to

While a number of metal sensitizing agents will fill'some of the foregoing requirements the of group II of the periodic table, namely mercury, cadmium and zinc. While either of these metalsmay be employed in our process, mercury will be preferred because of its availability, vapor pressure, activation energy, and other peculiar properties.

' Resonance lines,

the reactor jacket prior to the product in The process of the present invention is not limited to any particular type of equipment. The reaction has been carried out satisfactorily in an annular reactor consisting of a cylindrical outer Pyrex jacket provided with an inlet at one at the other end, the inner cylinder emanating light of the desired wave length. For example, when it is desired to employ mercury as the metallic sensitizer, a mercury vapor lamp emanating light of 2537 A. wave length is inserted as a concentric inner cylinder in the Pyrex jacket. When employing mercury as a sensitizer, the lamp should be operated in such a manner that an unreversed 253'7 A. line is obtained. A satisfactory lamp for such a purpose is, for example, a 15 watt germicidal lamp, or a lamp such as described in U. S. Patent 2,473,642 to Found et al.

When cadmium is used as the metallic sensitizer, a cadmium lamp may be employed. The reactor jacket may be surrounded with a suitable heating means such as an electric heater or a furnace. In converting a parafiinic hydrocarbon, the parafiinic hydrocarbon introduced into the jacket through theinlet, and the products or reaction are withdrawn through the outlet. In carrying out a mercury-sensitized reaction, a satisfactory method of maintaining the mercury sensitizer in the reactor has been to place a small amount of metallic mercury into beginning of the reaction. Other satisfactory methods of introducing metal sensitizer are known; for example, a carrier stream, consisting of the vaporized hydrocarbon feed, or a portion thereof or an inert gas, such as nitrogen, may be passed through a vessel containing the metal sensitizer in the liquid or vapor state prior to passing said carrier stream into the reactor.

Although it is desirable to hydrocarbon, the present invention is not limited to such. The feed stock may include two or more parafiinic hydrocarbons from which olefins having a greater number of carbon atom than the feed stock may be produced. It is desirable that the paraffinic hydrocarbon not be contaminated with impurities which may react with the feed or sensitizer to produce undesirable contaminating compounds in the product. For example, water vapor in low concentration may harmful to the reaction when a mercury sensitizer is employed but it may be harmful when cadmium is used as the sensitizer because cadmium is oxidized by water vapor. Also it is desirable to exclude reactive compounds other than the hydrocarbons because such compounds may cause undesirable side reactions to take place which will produce other compounds than the desired product.

The efliuent leaving the reaction zone, in the employ a purified vpractice of the present invention, may be subjected to condensation to recover the feed and the liquid phase, and hydrogen and in the gas phase and being easily separable therefrom. The condensed liquid phase ma v to fractional distillation to recover a desired fraction and the olefins may then be recovered from a segregated fraction by suitable chemical treatment which is well known in the art. For example, it is known that olefins react with sulfuric acid from which they are recoverable as such.

The invention will be further illustrated by reference to the following examples.

A substantially pure normal butane feed connot be taining about 98% normal butane and 2% other parafiins was charged to a reaction zone, such as that described before, including a 15 watt germicidal lamp. The temperatures employed ranged for one run from 120 to 130 F. and in the second run the temperature was 133 F. The contact time during which the butane was exposed to the radiation was around 4 minutes. Olefins were identified in both products having from 6 to 12 carbon atoms in the molecule. The olefins averaged about 8 carbon atoms in the molecule.

Additional runs were made in an watt 2537 mercury type lamp with normal butane as a feed stock. The temperature in the reaction zone was 125 F.; a yield of olefins of about 5% was found in the product having from 6 to 12 carbon atoms in the molecule.

In additional runs normal butane was exposed in a reaction zone including an 800 watt mercury lamp. The time the butane was exposed in these runs ranged from 0.5 to 3.3 seconds, the temperature remaining constant at 250 F. The results of these runs are shown in Table II.

From the data in Table II, it will be seen that the olefin concentration increases as the residence time increases at a constant intensity of radiaion.

Another run was made in a 2400 watt mercury which gaseous normal butane which had been saturated with mercury was charged thereto. The intensity of radiation was about 0.1 watt per square centimeter of reaction zone surface. The temperature in the reaction zone was above 600 F. The time the butane was exposed was about 3 seconds. The olefin content of the product was about 43% by volume. The product had from 6 to 12 carbon atoms in the molecule.

When employing mercury as a metal sensitizer, the product may be found to contain small quantities of mercury carried out from the reaction zone. It may be desirable, therefore, to recover this mercury and the mercury may be separated by cooling the effluent from the reaction zone or the effluent may be passed Over a suitable bed of amalgamating material to remove mercury from the product.

In the foregoing examples, the runs were carried out by vaporizing the feed and heating it to a reaction temperature and pressure. The feed was introduced into the inlet of an annular reactor of which a mercury lamp formed the inner cylinder and a Pyrex glass jacket formed the outer cylinder. The lamp employed has an energy output of over of the emitted radiation in the unreversed 2537 A. line. It? was convenient to place a small amount of liquid mercury in the annulus to supply mercury vapor to the hydrocarbons to act as a metal sensitizer for the reaction in the gases where the feed stock to maintain reaction temperature. were substantially atmospheric.

a metal sensitized photochemical reaction is ina resonance frequency radiation, to a resonance may then combine with a parafiinic hydrocarbon l5 200 to 506 F. at a pressure substantially atmosformation of an alkyl radical from the parafiinic said resonance frequency radiation correspondnumber of carbon atoms than the parafiin hydroatoms in a reaction zone, having a surface excarbon feed Regardless of the mechanism l'nposed to a resonance frequency radiation to a volved in the formation of an olefin having a resonance frequency radiation of an intensity in greater number of carbon atoms than the normal the range from O 1 to 4 watts per square centiparafi'in feed, it is to be understood that our meter of exposed reaction zone surface in the invention involves subJectmg a parafiinic hydropresence of a metal sensitizer selected from the carbon to the foregoing conditions to cause the group consisting of mercury, cadmium, and zinc formation of the higher molecular Weight olefins at a temperature in the range from 200 to 500 as has been described. F. for a time ranging from 0.5 second to 5 minutes The nature and objects of the present inven and at a pressure at least atmospheric to form tion having been completely described and illusa product comprising n l ns h vin a trated, what we wish to claim as new and useful greater number of carbon atoms than said parafand to secure by Letters Patent is: finic hydrocarbon, recovering said product, and

l. A method for producing olefins which comseparating mono-olefins therefrom, said resofinic hydrocarbon having from 2 to 6 carbon to one of the resonance lines of said sensitizer.

a cms In a reaction zone, having a surface ex- A method in accordance with claim 7 1n posed to a resonance frequency radiation, to a which the metal sensitizing agent is mercury. resonance frequency radiation in the range from A metho in accordance with claim 7 1n 0 1 to 4 Watts per square centimeter of exposed Whlch the metal sensitizing agent 15 zinc reaction zone surface in the presence of a metal 0 A method in accordance with claim 7 in sensitize: selected from he group consisting of which the metal sensitizing agent is cadmium mercury, cadmium, and Zinc at a temperature 11 A metho 1n accordance with claim 7 in 0.5 second to 5 minutes to form a product com- HENRY G. SCHUTZE. prising olefins having a greater number of car- HARRY E. CIER. bcn atoms than said paraifinic hydrocarbon, and I recovering said product, said resonance frequency Reffil'ellces Cited In the fi 0f thlS p n radiation corresponding at least to one of the UNITED STATES T N resonance lines of said sensitizer.

2. A method in accordance with claim 1 in gg T iwame F i which the metal sensitizing agent is mei cury. ay or e 3. A method in accordance with claim 1 in FOREIGN PATENTS which the metal sensitizing agent is zinc. Number country Date 4. A method in accordance with claim 1 in 307306 Great Britain Mar. 4 1929 vhich the metal sensitizing agent is cadmium.

5. A method for producing olefins which com- OTHER REFERENCES prises exposing a continuous stream of a paraf- Bates et al.: Journal American Chemical Socifinic hydrocarbon having from 2 to 6 carbon ety, vol. 49 (1927), pp. 2438-2456. atoms in a reaction zone, having a surface ex- Olson et a1.: Journal American Chemical Sociposed to a resonance frequency radiation, to a ety, vol. 48 (1926), pp. 389-396. resonance frequency radiation of an intensity Taylor et al.: Journal American Chemical in the range from 0.1 watt to 4 watts per square Society, vol. 51 (1929), pp. 2922-2936. centimeter of exposed reaction zone surface in Steacie et al.: Journal Chemical Physics, vol.

he presence of mercury at a temperature in the 12 (1944) pp. 34 36. range from 200 to 500 F. at a pressure sub- Le Roy: Canadian Chemistry and Process Instantially atmospheric for a time in the range dustries, June 1944, pp. 430431. 

1. A METHOD FOR PRODUCING OLEFINS WHICH COMPRISES EXPOSING A CONTINUOUS STREAM OF A PARAFFINIC HYDROCARBON HAVING FROM 2 TO 6 CARBON ATOMS IN A REACTION ZONE, HAVING A SURFACE EXOSED TO A RESONANCE FREQUENCY RADIATION, TO A RESONANCE FREQUENCY RADIATION IN THE RANGE FROM 0.1 TO 4 WATTS PER SQUARE CENTIMETER OF EXPOSED REACTION ZONE SURFACE IN THE PRESENCE OF A METAL SENSITIZER SELECTED FROM THE GROUP CONSISTING OF MERCURY, CADMIUM, AND ZINC AT A TEMPERATURE IN THE RANGE FROM 100* TO 750* F. AT A PRESSURE AT LEAST ATMOSPHERIC FOR A TIME IN THE RANGE FROM 0.5 SECOND TO 5 MINUTES TO FORM A PRODUCT COMPRISING OLEFINS HAVING A GREATER NUMBER OF CARBON ATOMS THAN SAID PARAFFINIC HYDROCARBON, AND RECOVERING SAID PRODUCT, SAID RESONANCE REQUENCY RADIATION CORRESPONDING AT LEAST TO ONE OF THE RESONANCE LINES OF SAID SENSITIZER. 